The invention relates to a device for releasing at least one substance. One particular embodiment constitutes a backing material and, applied at least partially thereon, a device in the form of an adhesive composition comprising the one or more active substances that are delivered to the skin.
Transdermal therapeutic systems (TTS) are forms of administration of medicaments that deliver one or more medicaments to the skin over a defined period at their location of use. A distinction is made here between systemic and local administration forms.
With systemic administration forms, the active substance passes through the skin into the bloodstream by diffusion and can act within the body as a whole. Local administration forms, on the other hand, act only at the sites of application. The active substance remains in the skin or in the underlying layers.
Strongly adhering plasters are normally coated over their entire area with a rubber adhesive composition. The sticking of such products to the skin gives rise, following their removal, to marked skin irritations and mechanical stressing of the skin. Without auxiliary media it is impossible to break the bond painlessly. In some cases, there are allergic reactions. Furthermore, the adhesive compositions used often lead to a transfer of composition onto the skin.
The use of skin-friendly adhesive compositions, such as acrylate adhesive compositions and hydrogels, is out of the question because of their low shear stability and tack. Improvement through aftertreatment, especially crosslinking, though possible, nevertheless gives a result which is unsatisfactory overall. The proprioreceptive effect is less than that of systems with a rubber adhesive composition.
Other known adhesive systems based on conventional block copolymers are however not skin-friendly, owing to the high level of stabilizer added, or because of the high levels of cohesiveness have been found suitable to date only for industrial applications; alternatively, they cannot be formulated for strong adhesion and sticking to the skin.
The abovementioned adhesive compositions are pressure-sensitive self-adhesive compositions which may be present in a carrier matrix for processing. The term carrier matrix is understood to refer to common organic or inorganic solvents or dispersion media.
Systems without a carrier matrix are referred to as 100% systems and are likewise not unknown. A common mode of processing is that of the melt. Pressure-sensitive hot melt adhesive compositions of this kind have also already been described in the prior art. They are based on natural or synthetic rubbers and/or other synthetic polymers.
An advantage of the 100% systems is that they avoid an operation of removing the carrier matrix, i.e. the auxiliary media, thereby raising the productivity of processing and at the same time reducing the expenditure on machinery and the energy costs. In addition, this reduces the occurrence of residues of the carrier matrix, which, in turn, is beneficial to a reduction in the allergenic potential.
Because of their high level of hardness, sticking to the skin is a problem for such 100% systems.
It is also known to apply such self-adhesive compositions not only over the entire area but also in the form of a pattern of dots, for example by screen printing (DE-C 42 37 252), in which case the dots of adhesive can also differ in their size and/or distribution (EP-B 353 972), or by intaglio printing, in lines which interconnect in the longitudinal and transverse directions (DE-C 43 08 649).
The advantage of the patterned application is that the adhesive materials, given an appropriately porous backing material, are permeable to air and water vapour and, in general, are readily redetachable.
A disadvantage of these products, however, is that if the area covered by the adhesive film, which is impermeable per se, is too large there is a correpsonding reduction in the permeability to air and water vapour; the consumption of adhesive composition rises, and, if the area covered by the adhesive film is small, the adhesion properties deteriorate, i.e. the product is detached too readily from the substrate, especially in the case of heavy, textile backing materials.
Numerous embodiments of active substance plasters have already been described in the prior art, some of them operating in accordance with the reservoir principle, where the active substance is delivered, for example, by way of a membrane, in some cases also with a matrix system or with a relatively complex multilayer structure.
It is also known that the adhesive composition of the plaster can be employed as the matrix comprising active substance. In addition to self-adhesive compositions applied from solution, hotmelt self-adhesive compositions have also been proposed for this purpose, as for example in EP-A 663 431, EP-A 452 034, EP-A 305 757, DE-A 43 10 012, DE-A 42 22 334 and DE-C 42 24 325. The active substances listed in these documents, if named at all, have been systemic ones.
Examples of active substance plasters are antimycotic and keratolytic active substance plasters and those which aid the circulation.
However, plasters of this kind, which occasionally have to be applied over a relatively large area, in some cases exhibit distinct mechanical skin irritations after removal in the case of sensitive patients. In some cases there are allergic reactions. After a prolonged period of wear, their removal is to some extent painful.
A further disadvantage of the known thermally active plasters with an adhesive composition based on natural rubber, which is applied in the form of a solution with organic solvents to the plaster backing, is the comparatively low rate of release of the active substance.
The abovementioned disadvantages, and more, also apply to active substance plasters comprising substances other than those mentioned.
For instance, WO 94/02123 describes an active substance plaster based on pressure-sensitive hotmelt adhesive compositions and comprising low-melting and/or readily volatile active substances in a concentration of from 2.5 to 25% by weight. The polymers employed in that document are A-B-A triblock styrene-ethylene-butylene-styrene block copolymers which are notable for low initial tack and low bond strength on skin.
EP 0 663 431 A2, EP 0 443 759 A3, EP 0 452 034 A2 and U.S. Pat. No. 5,371,128 describe uses of pressure-sensitive hotmelt adhesives, based on silicone, with diverse additives and in differentiated forms of construction.
DE 43 10 012 A1 describes the construction of a dermal therapeutic system from meltable poly(meth)acrylate mixtures.
In particular, difficulties are apparent in the release of two or more active substances from polymer systems formed from only one type of polymer. Systems with two or more types of polymer, however, are critical in terms of their compatibility.
DE 43 16 751 C1 describes a multi-chamber system for administering active substances.
EP 0 439 180 describes an active substance plaster for administering tolubuterol.
EP 0 305 757 describes an active substance plaster for administering nicotine.
EP 0 305 758 describes an active substance plaster for administering nitroglycerine.
EP 0 305 756 describes a device for releasing substances, and the preparation and use thereof.
DE 37 43 945 describes a device for delivering substances, and the preparation process. In the case of the pressure-sensitive hotmelt adhesive composition described, which is based on SIS, the device is not self-adhesive. The processing ranges indicated therein lie well below those of hotmelt adhesive compositions and for such systems described would not provide sufficient anchorage of the adhesive composition.
WO 96/22083 indicates a polyisobutylene adhesive for transdermal purposes, having a tackifier with a high glass transition point. The adhesive is not foamed.
JP 07-196505 describes the administration of indomethacin in hotmelt pressure-sensitive adhesives. In this case, a polyethylene foam is used as backing material.
EP 0 428 017 describes an adhesive composition based on SEBS and SEPS block copolymers. There is no description, however, of the release of substances with a local or systemic action.
U.S. Pat. No. 5,085,655 describes the use of SEPS block copolymers as a cohesive sticking system, especially of nappies and panty liners. The possibility of releasing substances is not described.
JP 09 188 865 describes a system based on synthetic block polymers. The release of substances is not described.
JP 08277382 describes a system based on SEPS which is used as a hotmelt adhesive composition for nappies and sanitary towels. The release of substances is not described.
JP 08209094 describes a system based on synthetic block polymers. The release of substances is not described.
JP 03160083 describes a system based on SEPS which is used as a hotmelt adhesive composition for nappies and sanitary towels. The release of substances is not described.
The object of the invention is therefore to provide a device which comprises one or more active substances and which, while avoiding the disadvantages known from the prior art, features a high level of efficacy, i.e. a relatively high rate of release, even in the case of different combinations of active substances, and good skin compatibility coupled with good adhesion. In addition, the device should be able to be prepared in a technically simple and environmentally compatible manner.
This object is achieved by a device for releasing substances as is set out in the main claim. The subclaims relate to advantageous embodiments of the devices of the invention. The invention also embraces processes for producing such devices.
The invention accordingly provides a device for releasing active substances which at a frequency of 0.1 rad/s has a glass transition temperature of less than 15xc2x0 C. and an SEPS block copolymer content of at least 3% by weight and comprises at least one locally or systemically acting substance, in the preferred embodiment a variety of active substances. The active substance or substances are not hyperaemic; furthermore, the device should not be foamed.
SEPS here stands for styrene-ethylene-propylene-styrene, comprising a block copolymer on the basis of polystyrene blocks (S) and blocks of hydrogenated polyisoprene (EP) or hydrogenated poly(butadiene-co-isoprene) (EEP). Diblocks, triblocks and multiblocks may be used.
In one advantageous embodiment the device has an A/B diblock fraction of more than 30%, preferably greater than 60%.
Preferably, the quantitative concentrations of the active substance or substances in the adhesive composition lie between 0.01 to [sic] about 60% by weight, preferably from 0.1 to 20% by weight.
By active substances in the context of the present invention are meant chemical elements and organic and inorganic compounds which are able to migrate from the constituents of a generic device that comprise them and so bring about a desired effect. Among the fields of use of the device of the invention, human and veterinary medicine are of particular importance, and in this context a configuration of the invention in plaster form is particularly preferred.
Typical active substancesxe2x80x94with no claim to completenessxe2x80x94for the production of plaster systems doped with active substance are, in the context of the present invention, as follows:
The active substances are dispersed in the device preferably in a thermal homogenizer, such as thermal mixers, thermal kneading apparatus, roll mills or screw systems, for example. The active substance can be added to the ready-produced device. The active substance can also, for example, be incorporated into an intermediate stage or into the initial mixture.
The device is advantageously an adhesive composition which in a particularly preferred embodiment is a hotmelt adhesive composition having an SEPS block copolymer fraction of at least 3% by weight. In one preferred embodiment, triblock copolymers are used. For specific devices, SEP diblock or multiblock polymers are advantageous.
The bonding properties can be adjusted depending on the field of use. In certain cases, strongly self-adhering systems or else systems with pressure-sensitive adhesion are required. To make these adjustments, appropriate additives are added to the polymer system, such as tackifier resins, plasticizers, stabilizers and other auxiliaries.
Their softening point should be higher than 50xc2x0 C., since the application temperature is generally at least 70xc2x0 C., preferably between 90 and 150xc2x0 C. If desired, subsequent crosslinking by irradiation with UV or electron beams may be appropriate. This depends on the specific composition of the main polymer or the additives thereto.
It is particularly advantageous for further polymers to be present in the device, these polymers preferably being based on block copolymers. Blends of block copolymers based on SEPS and SEBS, in particular, are notable for their diverse possibilities for variation, since the targeted reduction in the glass transition temperature of the self-adhesive composition, as a result of the selection of tackifiers, plasticizers, polymer molecule size and molecular distribution of the components employed, ensures the necessary bonding with the skin in a manner appropriate to their function, even at critical sites on the human locomotor system.
The high shear strength of the hotmelt self-adhesive composition is achieved by the cohesive character of the polymer. The good tack results from the range of tackifiers and plasticizers employed.
For systems which adhere particularly strongly the hotmelt self-adhesive composition is based preferably on block copolymers, especially A-B or A-B-A block copolymers or mixtures thereof. The hard phase A is primarily polystyrene or its derivatives and the soft phase B comprises at least one soft phase B based on ethylene, butylene, propylene, isoprene, butadiene or mixtures thereof.
As a further preference, the polymers and the device are constructed on the basis of diblock (A-B) and/or triblock (ABA) copolymers, with a fraction of diblock copolymers of less than 80% by weight.
The chain of phase B may also include sections of other types, such as isoprene, butadiene or similar substances, for example. Polystyrene blocks may also be present in the soft phase B, in an amount of up to 20% by weight. The overall proportion of styrene, however, should always be less than 35% by weight. Preference is given to styrene contents of between 3% by weight and 30% by weight, since a lower styrene content makes the adhesive composition smoother.
The controlled blending of diblock and triblock copolymers is particularly advantageous, preference being given to a proportion of diblock copolymers of less than 80% by weight.
The adhesive composition may also include auxiliaries for particular release, or to assist such release. Examples here are polypropylene glycol and polyethylene glycol.
In one advantageous embodiment, the hotmelt self-adhesive composition having a SEPS block copolymer proportion of at least 3% by weight has the composition indicated below:
from 3 to 90% by weight of block copolymers,
from 5 to 80% by weight of tackifiers, such as aliphatic hydrocarbon resins, hydrogenated terpene resins, hydrogenated hydrocarbon resins, cyclopentadiene resins, styrene-xcex1-methylstyrene resins and low molecular mass polyisobutylenes,
less than 60% by weight of plasticizers, such as paraffin oils, aliphatic hydrocarbon oils, waxes and fatty acetates and alcoholates,
less than 15% by weight of additives,
less than 20% by weight of active substance release auxiliaries, and
less than 5% by weight of stabilizers,
less than 60% by weight of active substance or substances.
The tackifiers and plasticizers serve to establish the bonding properties and the stability. If desired, further stabilizers and other auxiliaries are employed.
The following polymer/tackifier combinations are given by way of example.
Combinations of other polymer systems are obvious to the person skilled in the art.
It is possible to fill the adhesive composition with mineral fillers, fibres or hollow or solid microbeads.
The hotmelt self-adhesive composition has a softening point of more than 50xc2x0 C., preferably from 70 to 220xc2x0 C. and, with very particular preference, from 75 to 140xc2x0 C.
The dynamic glass transition temperature of the elastomer phase of the adhesive matrix, at a frequency of 0.1 rad/s, is less than 15xc2x0 C., preferably from xe2x88x923 to xe2x88x9230xc2x0 C. and, with particular preference, from xe2x88x929 to xe2x88x9225xc2x0 C.
Plasters in particular are subject to stringent requirements in terms of their bonding properties. For ideal application, the hotmelt self-adhesive composition should possess a high tack. There should be functionally appropriately bond strength to the skin and to the reverse of the backing. So that there is no slipping, the hotmelt self-adhesive composition is also required to be of high shear strength.
The targeted reduction in the glass transition temperature of the self-adhesive composition, as a result of the selection of the tackifiers, plasticizers, polymer molecule size and molecular distribution of the components employed, achieves the necessary bonding, appropriate to its function, with the skin and with the reverse of the backing.
The high shear strength of the self-adhesive composition employed here is achieved by the high cohesiveness of the block copolymer. The good tack arises from the range of tackifiers and plasticizers that is employed.
Product properties such as tack, glass transition temperature and shear stability can be quantified readily using a dynamomechanical frequency measurement. In this case, use is made of a rheometer controlled by shearing stress. The results of this measurement method give information on the physical properties of a substance by taking into account the viscoelastic component. In this instance, at a preset temperature, the hotmelt self-adhesive composition is set in oscillation between two plane-parallel plates with variable frequencies and low deformation (linear viscoelastic region). Via a pickup control unit, with computer resistance, the quotient (Q=tan xcex4) between the loss modulus (Gxe2x80x3, viscous component) and the storage modulus (Gxe2x80x2, elastic component) is measured.
Q=tan xcex4=Gxe2x80x3/Gxe2x80x2
A high frequency is chosen for the subjective sensing of the tack and a low frequency for the shear strength.
A high numerical value denotes better tack and poorer shear stability.
The complex-dynamic glass transition point is the point of transition from the amorphous to the viscoelastic region. It corresponds to the maximum of the temperature function at a predetermined frequency.
In accordance with the invention, preference is given to hotmelt self-adhesive compositions for which the ratio of the viscous component to the elastic component at a frequency of 100 rad/s at 25xc2x0 C. is greater than 0.7, or to hotmelt self-adhesive compositions for which the ratio of the viscous component to the elastic component at a frequency of 0.1 rad/s at 25xc2x0 C. is less than 0.6, preferably between 0.35 and 0.02 and, with very particular preference, between 0.3 and 0.1.
In exceptional cases, a modified use of the device can be achieved by it being foamed.
In this case, the devices with the active substances added to them are preferably foamed using inert gases such as nitrogen, carbon dioxide, noble gases, hydrocarbons or air, or mixtures of these. In some cases, foaming additionally by thermal decomposition of gas-evolving substances, such as azo, carbonate and hydrazide compounds, has been found suitable.
The degree of foaming, i.e. the gas content, should be at least about 5% by volume and can range up to about 85% by volume. In practice, levels of from 10 to 75% by volume, preferably 50% by volume, have been found appropriate. Operating at a relatively high temperature of approximately 100xc2x0 C. and with a comparatively high internal pressure produces very open-pored adhesive foam layers which are particularly permeable to air and water vapour.
The advantageous properties of the device include its good conformity even on uneven surfaces, owing to the elasticity and plasticity of the foamed device.
At the same time, the vacuoles in the foam bring about a more than proportional increase in the transportation of the active substances, as a result of which very good release rates are achieved.
A particularly suitable process for producing the device foamed in accordance with the invention operates by the foam mixing system. In this system, the thermoplastic adhesive composition is reacted with the intended gases, such as nitrogen, air or carbon dioxide, for example, in various volume proportions (from about 10 to 80% by volume) in a stator/rotor system under high pressure and at a temperature above the softening point (approximately 120xc2x0 C.).
Whereas the gas entry pressure is greater than 100 bar, the mixing pressures between gas and thermoplastic in the system are from 40 to 100 bar, preferably from 40 to 70 bar. The pressure-sensitive adhesive foam produced in this way can subsequently pass through a line into the applicator unit. In the applicator unit, commercially customary nozzles, extruder systems or chamber systems are used.
The interaction of the active substances with the skin is, as is known, modulated by enhancers that are mixed into the adhesive composition or intensified by the occlusive effect of adhesive composition and covering. In contrast to this it is possible, with the use of breathable doped coatings in conjunction with elastic and likewise breathable backing materials, in particular for example during sporting activities, to achieve
a) a level of wear comfort which is perceived subjectively as more pleasant by the user and
b) as a result of an interaction of the skin with the environment (for example suppression of perspiration) that is less disturbed by the release behaviour, a more defined penetration of active substances into the skin.
In contrast, it is also possible by virtue of the processes mentioned here to achieve permeability of the doped plaster system from the outside. By virtue of this property of the product, therefore, it is possible following actual application for substances to be brought to the contact point between doped adhesive/skin, through the backing, even at a later time (sprinkling on of liquid, wiping, etc.). These substances might, for example, comprise an additional enhancer effect or might initiate or attenuate the pharmaceutical action or modulate it appropriately for a favourable consumer response.
By virtue of the foaming of the device and the open pores in the composition which form as a result, and given the use of an inherently porous backing, the products coated with the device are of good permeability to water vapour and air. The amount of device required is considerably reduced without adverse effect and mode of action of the device properties [sic].
Foaming also generally reduces the viscosity of the device. This lowers the melt energy, and even thermally unstable backing materials can be coated directly.
It is also advantageous, especially for use with medical products, if the doped composition is applied partially to the backing material, for example by halftone printing, thermal screen printing, thermal flexographic printing or intaglio printing, because backing materials which have been self-adhesively treated in a continuous applied line may in adverse circumstances induce mechanical skin irritations when applied.
It is also possible, furthermore, to apply the adhesive composition, for example, by spraying, which produces a more or less irregular pattern of application.
Partial application makes it possible, through controlled channels, to dissipate the transepidermal water loss, and improves the removal of sweat from the skin in vapour form, especially when the backing materials used are permeable to air and water vapour. By this means the skins irritations induced by an accumulation of body fluids are avoided. The dissipation channels that have been set up enable fluids to be conducted away.
Preference is given to application in the form of polygeometric domes, especially those where the ratio of diameter to height is less than 5:1. Printed application of other forms and patterns on the backing material is also possiblexe2x80x94for example, a printed image in the form of alphanumeric character combinations or patterns such as matrices, stripes and zigzag lines.
The doped composition can be distributed uniformly over the backing material; alternatively, it can be applied with a thickness or density which varies over the area, as appropriate to the function of the product.
The principle of thermal screen printing consists in the use of a rotating, heated, seamless, drum-shaped, perforated, cylindrical screen which is fed via a nozzle with the preferred composition. A specially shaped nozzle lip (circular- or square-section coating bar) presses the composition, which is fed in via a channel, through the perforation of the screen wall and onto the backing web that is conveyed past it. This backing web is guided by means of a counterpressure roller against the external jacket of the heated screen drum at a rate which corresponds to the peripheral speed of the rotating screen drum.
In this process, the formation of the small doped domes takes place by the following mechanism:
The pressure of the nozzle coating bar conveys the doped composition through the screen perforation onto the backing material. The size of the domes formed is determined in advance by the diameter of the screen perforation. The screen is lifted from the backing in accordance with the rate of transportation of the backing web (rotary speed of the screen drum). As a consequence of the high adhesion of the self-adhesive composition and of the internal cohesion of the hotmelt, the limited supply of hotmelt self-adhesive composition in the perforations is drawn in sharp definition from the base of the domes, that is already adhering to the backing, and is conveyed onto the backing by the pressure of the coating bar.
Following the end of this transportation, the more or less highly curved surface of the dome forms over the predefined base area depending on the rheology of the hotmelt self-adhesive composition. The height-to-base ratio of the dome depends on the ratio of the perforation diameter to the wall thickness of the screen drum and on the physical properties (flow behaviour, surface tension and contact angle on the backing material) of the self-adhesive composition.
For the screen in thermal screen printing, the web-to-hole ratio can be less than 3:1, preferably less than or equal to 1:1 and, in particular, equal to 1:3.
The above-described mechanism of formation of the domes requires, preferentially, backing materials that are absorbent or at least wettable by the doped composition. Non-wetting backing surfaces must be pretreated by chemical or physical methods. This can be done by means of additional measures such as corona discharge, for example, or by coating with wetting agents.
Using the printing technique indicated it is possible to lay down the size and shape of the domes in a defined manner. The bond strength values which are relevant for use, which determine the quality of the products formed, are within very narrow tolerances provided that coating is carried out correctly. The base diameter of the domes can be chosen to be from 10 to 5000 xcexcm, the height of the domes is from 20 to 2000 xcexcm, preferably from 50 to 1000 xcexcm, the low-diameter range being intended for smooth backings and the range of greater diameter and greater dome height being intended for rough or highly porous backing materials.
The positioning of the domes on the backing is laid down in a defined manner by the geometry of the applicator unit, for example the gravure or screen geometry, which can be varied within wide limits. With the aid of the parameters indicated it is possible, by way of adjustable variables, to establish with very great precision the desired profile of properties of the coating, harmonized with the various backing materials and applications.
The backing material is preferably coated at a rate of more than 2 m/min, preferably from 20 to 220 m/min, the chosen coating temperature being greater than the softening point.
The doped device can be applied to the backing material with a weight per unit area of greater than 15 g/m2, preferably between 90 and 400 g/m2 and, with very particular preference, between 130 and 300 g/m2.
The percentage area that is coated with the doped device should be at least 20% and can range up to approximately 95%, for specific products preferably from 40 to 60% and from 70 to 95%. This can be achieved, if desired, by means of multiple application, with the possible use if desired of devices having different properties and dopes.
The combination of the doped devices and of the partial coating firstly ensures secure bonding of the medical product to the skin and secondly prevents at least visually discernible allergic or mechanical skin irritations, even in the case of an application which extends over several days.
The epilation of corresponding body regions and the transfer of composition to the skin are negligible owing to the high cohesiveness of the device, since the device is not anchored to skin and hairxe2x80x94rather, the anchorage of the device to the backing material, at up to 12 N/cm (sample width), is good for medical applications.
Because of the intended breakage points that have been formed in the coating, layers of skin are no longer displaced with one another or against one another in the course of detachment. The non-displacement of the layers of skin and the relatively low level of epilation lead to an unprecedented degree of painlessness in such strongly adhering systems. In addition, the individual biomechanical control, which results in a demonstrable reduction in the bond strength of this device, assists detachability.
Depending on the backing material and its temperature sensitivity, composition can be applied directly or can be applied first to an auxiliary support and then transferred to the ultimate backing.
Subsequent calendering of the coated product and/or pretreatment of the backing, such as corona irradiation, for better anchorage of the adhesive layer, may also be advantageous.
In addition, treating the composition by electron beam post-crosslinking or by UV irradiation can lead to an improvement in the desired properties.
Suitable backing materials are all rigid and elastic sheetlike structures of synthetic and natural raw materials. Preference is given to backing materials which, following the application of the adhesive composition, can be employed in such a way that they fulfil the characteristics of a functional dressing.
Examples are textiles such as wovens, knits, lays, nonwovens, laminates, nets, films, foams and papers. In addition, these materials can be pretreated or aftertreated. Common pretreatments are corona and hydrophobicization; customary aftertreatments are calendering, thermal conditioning, laminating, punching and covering.
The backing material coated with the composition can have an air permeability of greater than 1 cm3/(cm2*s), preferably greater than 15 cm3/(cm2*s) and, with very particular preference, greater than 70 cm3/(cm2*s), and a water vapour permeability of greater than 500 g/(m2*24 h), preferably greater than 1000 g/(m2*24 h) and, with very particular preference, greater than 2000 g/(m2*24 h).
Finally, following the coating operation, the device can be covered with an anti-adhesive backing material, such as siliconized paper, or provided with a wound pad or with padding.
Subsequently, the device is punched out in the desired size.
It is particularly advantageous if the device is sterilized, preferably by means of xcex3 (gamma) radiation. This is particularly suitable for subsequent sterilization of a block copolymer-based polymer system containing no double bonds. This applies in particular to the styrene-propylene-ethylene-styrene block copolymer of the invention. In this case the properties are not subject to any changes that are significant for the application.
The device of the invention can have a bond strength of at least 1.5 N/cm, in particular a bond strength of between 2.5 and 5 N/cm. Higher bond strengths may be achieved on other substrates.
The intention in the text below is to describe particularly advantageous embodiments of the invention, without wishing thereby unnecessarily to restrict the invention.
In accordance with the invention, example formulations for releasing various active substances were prepared. All formulations were prepared without solvent in a laboratory kneading apparatus at a temperature of between 90xc2x0 C. and 180xc2x0 C. The pharmaceutical active substance was added during the cooling phase at a temperature which in the case of solid pharmaceuticals was approximately 10xc2x0 C. above the respective melting point. The production of laboratory samples for testing the formulations was carried out with the aid of a hot press.